A few years ago I passed a small kidney stone and I have to say it was quite painful.
Yesterday I noticed some blood in my urine, after my run in the morning. It then seemed to clear up, but was there again after my second run. This can be running induced. I did feel some discomfort and felt that it might be a stone, however I also had the feeling that it might be some thing in my bladder. The blood problem has gone away and I am optimistic that every thing will be OK.
Sorry if I just grossed anyone out, but this is life and all it entails.